The present invention relates to a zoom lens, particularly one whose focal length range is extended.
Until now it was known to extend the zooming focal length range of a zoom lens by:
(1) a method in accordance with which the whole or a part of the relay lens group is exchanged,
(2) a method in accordance with which a part of the elements in the relay lens group is moved,
(3) a method in accordance with which a converter lens group is added inside of, in front of or behind the relay lens group,
(4) a method in accordance with which the focusing lens group is exchanged,
(5) a method in accordance with which a converter lens is attached in front of the zoom lens. Of the above methods, (1), (3), (4) and (5) are undesirable because of the poor exchange operability and the cost or the portability of the interchangeable lenses. Method (2) is disadvantageous because of the length and the weight of the total system, and because the relay lens group becomes unavoidably long.
Further, methods (1), (2) and (3) in accordance with which the focal length of relay lens is changeable, suffer the inconvenience that in 8 mm or 16 mm cine cameras in which the view finder light beam is branched between an afocal zoom part and a relay lens group, the image cannot be observed through the view finder after the focal length range has been changed.